Variant Management Requirement Perspective

Hello everyone

We have several project that has similar or same subsystems in a nutshell we have variants. I want to reuse requirements for variant management with requirement specification. I tried to insert the existed requirements when I create new req. spec for new variant but it change every where and it prevent the new revisions of the new req spec. As you know sometimes you need to change fundamental requirements which already used every requirement specification(variant). I want to update those requirements automatically. Than sometimes there are custom requirements(parameters) special for each variant. I dont want to changes wont affect the other similar requirements.  is there any suggestion or tutorial for requirement management and variant management at ENOVİA. Thanks for very much

Zahid